Screens



Nov. 5, 1968 i R. MALFROY 3,409QI33 SCREENS Filed May 23, 1966 2 Sheets-Sheet 1 lA/VE/VTOR REM) MILFRO) Attorney R. MALFROY Nov. 5, v 1968SCREENS 2 Sheets-Sheet 2 Filed May 23, 1966 United States Patent FiledMay 23, 1966, Ser. No. 558,163 Claims priority, applicatio1919France,May 26, 1965,

3 Claims. (a. 209-404 ABSTRACT OF THE DISCLOSURE Rectangular screenwhose frame is provided at each edge with a rotatable rod anchored to arespective edge of a perforate sheet which is stretched across theframe, rotation of any rod serving to tension the sheet in a directionperpendicular to the rod axis.

This invention relates to plansifters and similar equipment.

Plansifters and similar equipment incorporate a number of screens orsieves, each screen or sieve including a frame over which a metal gauzeor other woven material is stretched.

While the equipment is in use, the gauze stretches and has to besubsequently re-tensioned. This operation has been a diflicult onehitherto, particularly because the small amount of space left free atthe outside of the frame prevents the fitting of any complicated meansof anchorage for the gauze.

The object of the present invention is to provide a screen for use in aplansifter or like equipment, in which the gauze of the screen can betensioned very simply and effectively.

According to the present invention there is provided in a screen a framecomprising elongate members defining the outline of the screen, one ofsaid members having a longitudinal groove therein, a perforate flexiblesheet having edges, said sheet being stretched across said frame, anelongate element seated in said groove around which one of said edges iswound until said sheet is stretched across the frame to give a requireddegree of tightness, and means for locking against rotation saidelongate element in said groove, the latter means being advantageouslydisposed at one' end of said elongate element.

When the rod or other elongate element is turned, the gauze or otherperforate sheet is wound up and is thus stretched. As the groove orother elongate recess is situated at least partially in the supportingface of the side of the frame, the gauze reaches the rod, to all intentsand purposes, without passing over any sharp edges and is thereforeuniformly tensioned.

In one advantageous embodiment of the invention the means whereby therod is immobilized or otherwise locked are provided at one of its ends.For example, the rod may be circular in cross-section, except at oneend, where it is of polygonal cross-section and carries a ferrule with aprojecting tab.

In this case, the groove may be provided in the angle formed by thesupporting face and the outer side face of the frame. The two sides ofthe groove should preferably be at an angle of less than 90 to eachother.

Alternatively, the rod may be polygonal in cross-section and isimmobilized within the groove by a plate fixed to the frame and coveringthe groove.

Each edge of the gauze may simply be wound around its associated rod,its attachment to the rod depending on friction. It is preferable,however, to provide positive fixing, which, according to a furtherfeature of the invention, is achieved by means of an adhesive tape. Thisshould 3,409,133 Patented Nov. 5, 1968 preferably be of the transfertype, i.e. adhesive on both sides, which enables the rod to adhere.

Certain embodiments of screens in accordance with the invention will nowbe described, by way of example, with reference to the accompanyingdiagrammatic drawings, in which:

FIG. 1 is a plan of part of the frame of one embodiment of a screenaccording to my invention;

FIG. 2 is a view, drawn to an enlarged scale, showing details of part ofthe frame of FIG. 1, with groove cappings or covering strips omitted;

FIG. 3 is a cross-section on the line III-III of FIG. 2;

FIG. 4 is a section similar to FIGURE 3 but shows a second embodiment ofthe screen;

FIGS. 5 and 6 are also sections similar to FIG. 3 but show two furtherembodiments;

FIG. 7 is a cross-section on the line VII-VII of FIG. 2;

FIG. 8 is a perspective view showing how the gauze may be attached toeach of the rods of the screen with adhesive tape; and

FIG. 9 is a cross-section showing how tape of transfer type may be usedfor fixing the gauze to one of the rods.

The screen illustrated in FIGS. 1-3 and 7 comprises a wooden or metalframe 1, over which a metal gauze (or a natural or synthetic wovenmaterial) 2 is stretched.

Each member of the frame 1 has a groove or other elongate recess 3, ofsquare section in the example illustrated, at the angle formed by thesupporting face of the frame, here assumed to be the upper face, withthe outer side face of the frame. The corresponding edge of the gauze 2is wound round and fixed to a rod or other elongate element 4, whichfits into the groove 3. The rod 4 is circular in cross-section, exceptat one end 4a, where it is of square section, and is secured in thedesired position by a tab 5 on a ferrule fitted over its square end,which tab bears against a recess 9 in the frame.

The gauze is tensioned by rotation of each of the rods 4 with the aid ofa suitably shaped spanner until the desired tension is obtained,whereupon a locking means in the form of the ferrule-carrying tab 5 isslipped over the square-section end of the rod.

The gauze 2 then exerts a force holding each of the rods 4 onto an innerface 312 of the groove 3. In this way, the rods are held in theirgrooves with little likelihood of being dislodged. As seen in FIG. 3,the plane of the upper face of frame 1 is substantially tangent to rod 4whereby the gauze 2 can be wound up without scraping against an edge ofthe frame.

As a further safeguard, the two sides of the groove 3 may include anacute angle with each other, as shown in FIG. 4 where the modified framehas been designated 1'.

For the sake of appearance and cleanliness, the groove 3 may be coveredwith a capping 6 shown in FIG. 3 as an angle member, which may forexample simply be fitted over the edge of the frame.

The embodiment shown in FIG. 5 differs from that illustrated in FIG. 3only in that the groove 3 is provided in the upper face of the side ofthe frame 1, capping 6 being here a flat cover plate screwed to thisframe in cantilever fashion.

In the embodiment shown in FIG. 6,rod 4' is polygonal or square incross-section throughout. The groove 3 is provided in the upper face ofthe frame and contains a resilient bed 7.

The torque exerted by the gauze 2 and the resilient bed tends to forceone edge of the rod 4' against the groove face 3a and another edgeagainst the capping 6, which is necessary in this embodiment to preventthe rod from turning. To increase the tension on the gauze, the

rod is rotated with the aid of a spanner slipped over one of its ends;the rod moves down in the groove, compressing the resilient bed 7, untilthe edge originally bearing against the face 3a is clear of capping 6'.The spanner is then released, whereupon this edge is now forced againstthe capping, locking the rod in its new position.

As already stated, if the rod 4 or 4 and the gauze 2 have sufiicientlyhigh coefiicients of friction, the gauze may be secured to the rod byfriction if wound around a sufficient number of times. It is better,however, to fasten the gauze to the rod. Adhesive tape may be used forthis purpose.

In FIG. 8, adhesive tape 8 has one part fixed to the rod 4, the gauze 2then being stuck to the remaining part of the tape while being stretchedlengthwise, as indicated by arrows f This pre-stretching avoids theformation of wrinkles in the gauze when this is subsequently stretchedin the direction of arrow f by the rotation of the rod 4.

In FIG. 9, transfer tape 8', coated with adhesive on both faces, hasbeen stuck to the rod 4. All that remains to be done is to apply thegauze 2, while keeping it stretched, to the rod 4, which has itself thusbeen rendered adhesive.

It should be emphasized that the invention is not limited to theembodiment described and illustrated here, but includes allmodifications thereof fairly embraced by the language of the appendedclaims.

What is claimed is:

1. In a screen, in combination:

A frame comprising elongate members defining the outline of the screen,at least one of said members having a longitudinal groove therein;

a cover member on said frame overlaying said groove;

a perforate flexible sheet stretched across said frame:

an elongate element rotatably seated in said groove in engagement withan edge of said sheet for tightening same across the frame; and lockingmeans for holding said elongate elment against rotation in said groove,said locking means including resilient means in said groove biasing saidelement against said cover member. 2. The combination defined in claim 1wherein said cover member is a cantilevered plate.

3. The combination defined in claim 2 wherein said resilient meanscomprises a layer parallel to said plate, said element being a polygonalrod sandwiched between said layer and said plate.

References Cited UNITED STATES PATENTS 629,933 8/1899 Spalckhaver101-4151 1,616,917 2/1927 Mueller 209403 1,895,309 1/1933 Boomershine101415.1 X 1,906,603 5/1933 Hungerford 209403 X 2,375,603 5/1945 Willard101-4l5.1 2,727,463 12/1955 Foster 1014l5.1 2,775,199 12/1956 Clalf etal. 101-415.1 2,848,109 8/1958 Pruitt 209319 X 3,022,728 2/1962 Heller10l415.1

FOREIGN PATENTS 238,402 8/ 1925 Great Britain.

811,054 3/1959 Great Britain.

OTHER REFERENCES Netzel, German printed application 1,008,257, 5/57,209403.

HARRY B. THORNTON, Primary Examiner. T. R. MILES, Assistant Examiner.

